Determine whether each of these arguments is valid. If an argument is correct, what rule of inference is being used? If it is not, what logical error occurs?
a) If n is a real number such that n > 1, then n2 > 1.
Suppose that n2 > 1. Then n > 1.
b) If n is a real number with n > 3, then n2 > 9.
Suppose that n2 ≤ 9. Then n ≤ 3.
c) If n is a real number with n > 2, then n2 > 4.
Suppose that n ≤ 2. Then n2 ≤ 4.